One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,8)(3,6,4,7)(9,10,13,16)(11,14,18,22)(12,15,20,24)(17,21,19,23)(25,26,31,29,30,34,28,33)(27,35,38,32,37,39,36,40)(1,3,5,4)(2,6,8,7)(9,11)(10,14)(12,19)(13,18)(15,23)(16,22)(17,20)(21,24)(25,27,30,37)(26,32,34,40)(28,38,31,36)(29,35,33,39)(1,3,5,4)(2,7,8,6)(9,12,13,20)(10,15,16,24)(11,17,18,19)(14,21,22,23)(25,28,30,31)(26,29,34,33)(27,36,37,38)(32,39,40,35)(1,3,5,4)(2,6,8,7)(12,20)(15,24)(17,19)(21,23)(25,29,31,34,30,33,28,26)(27,32,38,39,37,40,36,35)(1,4,5,3)(2,7,8,6)(10,16)(11,18)(15,24)(17,19)(27,37)(32,40)(35,39)(36,38)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.